Sunday, November 30, 2008

As any knowledgeable fifth-grader could tell you, few of the dinosaurs in the movie Jurassic Park had anything to do with the Jurassic Period. Most of the species in the movie lived during the Cretaceous Period, many millions of years later, including the velociraptors, tyrannosaurs, triceratops, and the ornithomimus herd. Offhand the only Jurassic dinosaurs I can recall from the movie were the massive brachiosaurs that occupied just a few scenes. The premise (from the sequels anyway) of the animals living in some kind of ecologically balanced paradise would be unlikely at best. The mixing of predator and prey species from long separated periods would lead to disaster, as most of the species would have no evolved defenses to predator attack methods. And of course, the whole "reconstitute a dinosaur" from old dinosaur DNA mixed with frog DNA idea is a real stretch anyway, although interesting results are coming from research with wooly mammoth DNA.

In any case, we continue onwards on our march through the geology of the Colorado Plateau. Cretaceous sediments are an important part of the Colorado Plateau sequence, and they reveal a changing world, including new plants (the angiosperms), a host of diverse new dinosaur species and many other animals. At the end of the period, the dinosaurs (and many other species) disappeared forever and a new world emerged in the Plateau country. A final transgression and regression of a shallow sea was followed by widespread deformation of the crust, and the rise of the region above sea level. The most recent era, the Cenozoic, our own time period, was beginning.

The Cretaceous formations of the Colorado Plateau are not as colorful as the Jurassic and Triassic sediments, but several national parks and monuments have been established in areas containing Cretaceous sediments, and in some cases the scenery is quite spectacular. Grand Staircase-Escalante National Monument and Capitol Reef National Park are two of the more striking examples, but other parks that are not really known for their rocks are also notable, including Mesa Verde National Park, Chaco Culture National Historical Park, Hovenweep National Monument, and Canyons of the Ancients National Monument. Important formations include the Cedar Mountain Formation, the Dakota Sandstone, the Mancos Shale, and the Mesa Verde Group.Today's photograph is a sunset view of Fajada Butte in Chaco Canyon, one of the eeriest (but not in the scary sense) parks I've ever visited on the Plateau. The rocks are part of the Mesa Verde Group.

Tuesday, November 25, 2008

I only provided one picture of Pinnacles National Monument in California's Coast Ranges in my previous post, and it showed none of the scenery that makes the park a special place. So here are two views of the 22 million-year-old rhyolite composite volcano that was erupted, sliced in half by the San Andreas fault, faulted into a graben structure, exhumed by uplift, and eroded by water and wind and mass-wasting into a beautiful parkland.

The first photo is a view from the High Peaks Trail, a marvelous 5 mile loop through the heart of the park. The walk across the ridgeline is just stunning. In many places, footholds had to be scooped out of the rock to provide access, although the exposure level is not too frightening (nothing like Angels Landing in Zion, for instance). On a clear day, the far ridges extend forever into the distance, while the giant monoliths of rhyolite dominate the foreground. This hike, along with the trail to Delicate Arch, and the climb of Angels Landing, is one of my favorite hikes in the world.

The second shot is a view of the previously mentioned high peaks from the perspective of the south end of the park on the trail to the Chalone Peaks. The High Peaks Trail winds along the spine of the ridge in the center of the photo, and has connecting points to trailheads on both sides of the park (no roads cross the park, so one must choose to visit from the west or the east side).

The third photo is one of the wild denizens of the park, an old Tom Turkey. I have a feeling this bird would have issues with a certain recent vice-presidential candidate. I have seen a lot of wildlife in the park, include a huge flock of wild turkeys, four or five California Condors, huge numbers of woodpeckers, the standard deer and various rodents, and my favorite, a huge bobcat. The cat was hanging out near the edge of the campground near the road, and as we approached on the highway, what I thought was a feral kitty-cat seemed to grow larger and larger until I finally realized what it was and grabbed for my camera. Too late of course. And I can't help but look for the cat at the same spot every time I pass by during subsequent trips, camera ready in hand.

I hope everyone in the geoblogosphere has a fine Thanksgiving, even if you are not in the particular country that celebrates the day. Times are toughening up for many of us, but here's wishing that we all weather the storm, and that the job situation brightens for those of you who are between jobs and searching for employment. Best wishes to all of you.

Sunday, November 23, 2008

Breccia? You betcha! Looking for Detachment has a fondness for breccias, and mentions a few others who think likewise. My field trip season never seemed to end this year (that's not a complaint), as I had two lab field trips to see the Del Puerto Canyon ophiolite this week, and a Saturday field trip to Pinnacles National Monument in the California Coast Ranges. It was a great trip for breccia bloviating.

Pinnacles is a marvelous, if widely unrecognized little park about 30 miles south of the town of Hollister. It was established as a national monument in 1908 by Teddy Roosevelt for the tower-like peaks of rhyolite lava flows and breccias that are quite out of character with the normally rounded hills of the Coast Ranges. Those who sponsored the park for protection were unaware of the deeper geological significance of the park.

The great San Francisco Earthquake of 1906 brought worldwide attention to the San Andreas fault. Extending from the Imperial Valley of southern California to Mendocino on the northern California coast, it is one of the more extensive fault systems on the globe, and it has generated two major historical quakes (1906 and 1857), and a more recent "moderate" quake (Loma Prieta in 1989). Paleoseismicity studies have revealed dozens of major earthquakes during the last few thousand years.

Prior to the advent of plate tectonics theory in the 1960's, large scale lateral movements were not considered possible on faults like the San Andreas, though it was clear that the most recent movements had indeed been lateral. A seminal paper in 1953 by Hill and Dibblee argued that the fault had shifted hundreds of miles since Cretaceous time, a highly controversial assertion for the time. In the decades that followed, the San Andreas came to be understood as a continental transform boundary between the North American and Pacific Plates. Still, the fault researchers hoped to find an unequivocal piercing point that would allow a direct measure of the exact amount of movement on the fault.

The Pinnacles volcano was a rhyolite composite cone that happened to erupt on the San Andreas fault about 22 million years ago. The San Andreas ripped the volcano apart, and the two halves began moving apart, 10 or 15 feet at a time during large earthquakes. In 1976, V. Matthews demonstrated that the Pinnacles rocks were virtually identical to the Neenach Volcanics in the Transverse Ranges of Southern California. The two halves were separated by 195 miles!

The park has a lot of offer visitors. An extensive trail system bisects the park, including two sections that explore underground caves formed by boulders piling into the narrow slot canyons carved into the rhyolite. The vertical rock faces are a climber's paradise, as shown in the photo above. The rhyolite breccia (formed from volcanic mudflows, also known as lahars) makes for lots and lots of toe-holds!

I once was privileged to introduce the famous rock-climber Royal Robbins when he spoke to a group of geology teachers in Modesto. I made a point that geologists know a great deal about the properties of rocks, but how many of us stake our lives on our understanding of those rocks? Rock climbers do that every day...

Saturday, November 22, 2008

Via the Yosemite Blog, the National Park Service has decided to permanently close down about a third of the tent cabins and other facilities in the Curry Village area of Yosemite Valley. The decision follows a series of rock falls over the last few years that have killed or injured several people. Investigations are seeking an explanation for an increase in incidents below the cliffs of the Glacier Point area.

The photo of the day shows some of the trees at Happy Isles that were snapped off by a huge rock fall in 1996 that killed one person and damaged the Nature Center.

Tuesday, November 18, 2008

I had one of those nice "convergence" moments today...I was discussing mass wasting in my physical geology classes today, and this story showed up on the front page of my local paper concerning the danger of rock falls in Yosemite Valley.

There was a rather nasty mass wasting event in the valley last month, and it has been noted that there have been four times as many rockfalls since 1996 than in the previous 139 (although I seriously wonder if this is because more attention is being paid to such events in recent years). If this is a true increase in the number of incidents, then the speculation that human interference is a causitive factor needs to be investigated. Most of the attention centers on water use at Glacier Point, the spectacular overlook on the rim of the valley. Some of the recent events have occurred in summer when visitation (and therefore water use) at the point is highest. Other researchers, including the park geologist, disagree with the contention that water plays a part in the recent events.

The other controversy concerns the placement of cabin units in Curry Village where many of the incidents have taken place. Curry Village took a hit when flooding in 1997 destroyed dozens of cabins, and proposals to remove more from the base area of the cliff would decrease housing units even more.

It was a great teaching moment...except that only four of my students had looked at a newspaper this morning.

Sunday, November 16, 2008

A great many parks on the Colorado Plateau draw their scenery from Jurassic-aged sediments, and have been reviewed on a fair number of posts in the last month or two (see here for a listing). I haven't said much about the dinosaurs themselves because I was waiting to talk about the ultimate dinosaur park: Dinosaur National Monument (a most creative name, don't you think?)

The park draws its fame for an extraordinary bone bed that was discovered in 1909 by Earl Douglass. Although thousands of bones were quarried and sent to distant museums, there was enough foresight among the powers-that-were to preserve hundreds of bones in place where they could be viewed in situ by the public. By 1915, 80 acres around the quarry were set aside as a monument by President Woodrow Wilson. The park was expanded in 1938 to include the spectacular gorges of the Yampa and Green Rivers, an area of some 200,000 acres. The park was the setting of one of the seminal battles in the nascent environmental movement in the 1950's when an effort to construct a huge reservoir in Echo Park in the heart of the monument was turned back (some details here).

The source of most of the dinosaur fossils in the monument is the Morrison Formation, one of the most widespread sedimentary units in the western United States. It is exposed over a region extending from Canada to New Mexico and from the Great Plains to Arizona and Utah, forming a unique badlands topography in shades of purple, red, green and yellow. The rocks reveal a vast river floodplain system that was occasionally mantled with volcanic ash from eruptions of stratovolcanoes to the south and west. A shallow sea existed to the north.

Rivers are wonderful settings for the preservation of fossils. Animals are drawn, of course, to river (fluvial) environments, and occasional floods will trap many of them. As rivers meander back and forth across the plains, point bars (inside loop of a meander) become collection points for animal carcasses. They can be quickly buried and preserved in such situations (the bone bed at Dinosaur NM is an example of this). The muds of the floodplains likewise can be a tomb for mired animals. In other situations, the muds served as nesting grounds for some species, and nests, egg shells and juvenile dinosaurs are counted among of the significant finds in the Morrison.

A phenomenal number of fossils have been found in the Morrison Formation, including dozens of species of dinosaurs, as well as smaller reptiles, pterosaurs, crocodiles, primitive mammals, fish, amphibians, and invertebrates. Many of the most best-known dinosaurs were discovered in the formation: stegosaurs, sauropods ("long-necks" to you parents out there), and allosaurs. Twelve species have been discovered in Dinosaur National Monument alone, including the Camarasaurus in the third photo above.

The clay-rich nature of the Morrison Formation has been the undoing of the most famous aspect of the park. The bone bed was exposed in a steep face that came to be protected under a three-story-high shelter. Over the years the soils have settled and the structure was seriously compromised, with cracks and fissures in the building that represented a danger to the staff and public. As a result, the building has been closed since 2006. Unfortunately, park visitation plummeted, and the budget situation at the park has deteriorated.

Because of the budget shortfalls, some political controversies have arisen in recent months over the management of Dinosaur National Monument and the role of paleontologists in the work force at the park. Rebecca at Dinochick Blogs has been on top of the issue, with the most recent flurry of letters here.

If you have the opportunity to visit the park, do not miss the 200,000 acres of the park that are not the fossil exposures! A vast plunging anticline dominates the park, and the two rivers that cross the anticline have carved deep gorges that are extremely popular with river rafters. A road climbs from the south boundary of the park to spectacular overlooks at Harpers Corner and above Echo Park.

Today's choices include a weasel I saw on the trail to the summit of Lassen Peak in northern California last year. It looked like a ground squirrel popping in and out of the rocks, but I realized it was probably looking for squirrels. I had never seen one of these before, so I kinda forgot about climbing Lassen (been there, done that; oh, for shame!), and sat down and waited. After about 30 minutes I got the shot I was hoping for. I wasn't that close, but I have a 12x zoom to work with. (Correction 12-11-09: it's actually an American Pine Marten; I don't know these furry animals as well as I should)

The second photo is a gopher snake I ran across during an eastern Sierra Nevada field trip in 2006. Reptiles seem so alien, especially seen up close. I can relate to thinking like a weasel, but reptilian brains are beyond me.

It recalled one of my other snake stories...one time I was driving a road on the outskirts of town and saw a juvenile snake in the roadway in eminent danger of being run over. I decided to do the nice thing and pick it up and put it in the nearby field. I looked at it very carefully (I live in rattler country, after all). No vee-shaped head; check. No rattles on the tail; check. Can't be a rattler, so I pick it up.

Its tail started rattling, and the head was magically vee-shaped, and it was trying to bite me!

I threw the snake into the field as fast as I could and went home and went on the internet. I knew gopher snakes often rattle their tails, and that they have a vicious disposition when picked up, but it was news to me that they can actually flatten their skulls to look like a rattlesnake!

It would have been an embarrassing story to tell in the emergency room...

The third is an owl I saw deep in the forest at Muir Woods National Monument, north of San Francisco. It was hard to photograph in the dark shadows, and I wasted a lot of digital space trying to get it. I really wondered if I had finally seen the elusive Spotted Owl. As it turns out, it was probably a Barred Owl, which is a somewhat invasive species that takes over from Spotted Owls in second-growth forests. Just the same it was a beautiful bird.

Sunday, November 9, 2008

I didn't really mean to leave everyone hanging in the Jurassic during our months-long tour of the geology of the Colorado Plateau, but I am easily distracted by things like work and politics. I want to at least make it out of the Mesozoic era before Thanksgiving, so I am picking up the thread where we left off on Oct. 17 with a visit to Arches National Park.

The stratigraphy of the park is relatively straightforward: the visible scenery mainly includes the Navajo Sandstone, the Dewey Bridge member of the Entrada Sandstone, and the Slickrock member of the Entrada. The Navajo Sandstone has a huge role in the scenery of other parks on the Plateau (see discussions here), but is mostly muted here. It is familiar to park tourists as the "petrified sand dunes" that can seen along the road in the south part of the park, and the very dramatic white rock along the park entrance road. The Dewey Bridge member is a "crinkly" layer of sand, silt and gypsum at the base of many of the arches. The reason for the deformed layers is unclear. One intriguing proposal is that a nearby asteroid impact distorted the layers (Upheaval Dome in Canyonlands National Park is the proposed impact site). Most of the arches occur in the Slickrock member, a cliff-forming layer that is obvious throughout the park.

The origin of the park's famous arches (there are hundreds) is tied to the salts of the Paradox Basin discussed earlier in this post. The salt beds are thousands of feet thick, and when placed under pressure, can slowly flow upwards through the overlying rock, forming domes and anticlines (upward pointing folds). Over millions of years, erosion removed thousands of feet of overlying sediment, and the salt was close enough to the surface to be affected by groundwater: it was dissolved away. The tops of the folds collapsed inwards, and the Entrada Sandstone was fractured (jointing) into a series of parallel fins. A large northwest trending anticline crosses the park; most of the arches occur along the flanks of the anticline.

The top of the fins are exposed to the arid desert climate, where the rock dries quickly following the infrequent storms. At the base of the fins, where the rock is buried by soil and loose sand, the rock may stay moist much longer. This leads to the solution of the cement holding the sandstone together, and the fins start to weather from below. Eventually a small window may open up, and falling slabs of rock enlarge the opening. The largest arch, Landscape, has an opening the length of a football field. Unfortunately, it is so thin and fractured that it may not last our lifetimes (it is in the third picture of the day). A large chunk fell about fifteen years ago. Wall Arch, another arch in the same area, just collapsed last summer.

Today's first photograph shows a small arch in the vicinity of Delicate Arch (a corner of Delicate is visible on the left side). The foreground includes tilted layers of the Entrada where they collapsed into the salt anticline. The La Sal Mountains can be seen in the distance.

The second photo shows my nomination for one of the most dramatic trails in existence, the one that leads to Delicate Arch. This is definitely a case where the end of the trail is not the main attraction; the whole trail is a treat, from one end to the other.

Unfortunately, politics and politicians don't stop politicking, elections or not. Arches, like the Grand Canyon is being threatened by the possibility of gas drilling just outside the park boundaries. The outgoing administration seems to be trying to run a fire sale on leases before they leave office in January. It is especially irritating that the Bureau of Land Management seems to be trying to fly under the public radar in their announcements. More information on the issue (and maps of the proposed leases) can be found here.

Friday, November 7, 2008

The question of the day concerns animals in the field...catch posts here and here. I was immediately reminded of a long-running discussion between my son and I about cows and whether cows are planning to take us over as the dominant species on the planet (recall the dolphins and mice of Hitchhikers Guide to the Universe). Some people think our country will be taken over by black helicopters; my son is more convinced it will be black cows.

I have disagreed in the past. I felt large roosters were the true threat. I especially think of one I met at Pipe Springs National Monument that I named Tyrannosaurus pecks (no pictures though, I was running away). The wounds were painful...

During an exploration of some wild caves in the Sierra Nevada foothills, I found my assumptions about chickens to be wrong. Rounding a corner, we were faced with a vanguard of the coming invasion...I had the same feeling that King Arthur must have experienced when he met the Knights Who Say Nit (Monty Python's Holy Grail), or maybe the white rabbit.

Seriously though, there are some great caves in our neck of the wood. I have a smattering of photos posted here. One of our Sierra caves (Lilburn in Kings Canyon National Park) has something like 17 miles of passageways. Info on caves of Sequoia and Kings Canyon can be found here.

Thursday, November 6, 2008

A kind of 'mini-meme' developed in the last few days as many geobloggers from the U.S. (and a few others, I'm sure) were carefully watching the returns from the presidential elections. It has involved the relationship of geology to politics.

Brian at Clastic Detritus noticed a correspondence between counties who increased their Republican vote, and the location of the Appalachian Orogen. No geologic explanation for the Arizona vote is clear, however.

Eric at Dynamic Earth noted some shocking deficiencies on the part of one of the candidates on her ignorance of Africa and the signatories to NAFTA (the North America Free Trade Agreement; there are only three countries in North America to choose from...). Admittedly, this post is more about geography, but there is a 'geo' in there. [UPDATE: I sort of fail the "three countries in NA; there are quite a few island nations and territories, i.e. Greenland, Bermudas, etc. that are included with North America. I was thinking in continental terms]

Callan Bentley at NOVA Geoblog has a link to a map of the US that is tied not to geography, but to the proportion and influence of voters. If you thought the election was crazy, this map is on drugs. BTW, way to go Virginia!

In my last post I was using a flood analogy to express my hopes for the outcome of the election, talking also of landslides and tsunamis. It gave me this great idea of blogging on the use of geologic terms in describing politics and other social phenomena. I started to develop the idea in more detail, and then happened upon Lee Allison's Arizona Geology blog. He beat me to the punch in a big way: check it out here, and here. Lee also has a couple of great posts on politicians who started out as geologists, here and here. I had no idea that Colin Powell had a geology degree, but I bet it helped during the planning for the first Iraq war. Herbert Hoover I knew about; I remember reading a story of his fight for reimbursement from the USGS:

"A favorite story deals with his job as disbursing officer for a United States Geological Survey party. When a pack mule was found dead, the rules required Hoover and two witnesses to investigate the cause of death. They found a loose hind shoe caught in the animal's neck halter. So they reported that it had broken its neck while scratching its head with a hind foot. The bureau in Washington refused to accept this “tall story,” and charged the party $60 for the lost animal. From that time on Hoover watched mules to confirm the fact that they could scratch their heads with a hind foot."

I hope this gets the politics out of my system for now. I know I am sick and need help; this morning I actually clicked on this:

Today's photo represents change happening "at a glacial pace", and shows the Saskatchewan Glacier in Banff National Park in Alberta, Canada. It has a source in the Columbia Icefield, and along with the Athabasca Glacier shows the effects of global warming, having retreated over a mile in the last century.

Tuesday, November 4, 2008

One more picture from last Saturday, and a look at the anatomy of a fall flood event in Yosemite Valley. I doubt any damage was done, since the high flow was average for a normal spring runoff day in April. But not for November! The river went from around 20 cubic feet per second to a record 1,160 cfs in a matter of hours as a result of a warm storm. The previous record was around 650 cfs for the date. The rushing waters were dark with mud and dirt that had accumulated in the riverbeds for the last six months or so of no rain and low river flows. A cleansing was taking place.

I realize this will be a clumsy analogy, but I am hoping that this day, November 4, will be an unexpected flood of a different kind. I blog because I love geology and I want to share my stories and my pictures with whoever finds them interesting. But I learned blogging from politics...I am a political junkie at heart, and for years I waited for news from newspapers (in the really olden days), and from 24 hour cable news (in the somewhat less olden days), and from the internet over the last couple of years. For months now, I have haunted the internet "tubes" for every tidbit of evidence that the political winds in my country are finally changing. And I feel like a storm is coming, one that will cleanse this country of the filth that has accumulated over the last eight years.

How is it that a country that stands for freedom and justice and equality ended up in an unjustified and tragic war of choice that has killed more than 4,000 of our best? How did we end up as a country that imprisons people without due process, and which condones torture? When did we tear up our own constitution?

I have been waiting for my country to wake up and repudiate those who have subverted justice and law to their own ends. There is hope, in that the current occupant of the White House has the lowest approval ratings in polls ever recorded. There is hope that the Senate and House fell into the hands of a different party in 2006, even though they haven't accomplished much in these two years. But most of all I find hope that a good man named Barack Obama stands at the threshold of being elected president. He has been the target of one of the slimiest and most negative political campaigns ever conducted in American history, and has fought back with grace and leadership. I would never have thought a moment in history like this was possible. But maybe, maybe this day it will happen. I hope for a landslide, a flood, a tsunami, to wash away the stains that Bush and Cheney have left on our reputation as a country of justice and law.

Be sure to vote today. If they try to stop you with long lines, with too few voting machines, or electronic machines that don't accurately record your choices, fight for your right to have your vote counted. Don't be intimidated. Voting is a right that many have died for, and this day no one can deny you.

Sunday, November 2, 2008

I was in Yosemite Valley yesterday with our campus Geology Club; it was raining, rather heavily at times. Did it spoil our trip? Not by a long shot...it was a hardy crew who knew it would be wet. It turned out to be one of my finest trips ever (and those who follow this blog know I am there a lot!). Fall in Yosemite means lots of beautiful color in the trees, but waterfalls are generally expected to be dry. Instead, for us, Yosemite Falls was a mere trickle at noon, but by three o'clock, they were booming like it was spring runoff. Apparently we witnessed a record set by the Merced River. It rose in one day from 20 cubic feet per second to 1,160 cubic feet per second (the previous high flow record for November 1 was 645 cfs; current data is here). And it looked the part, the water was brown and sudsy and full of debris. It was an extraordinary privilege to be in the Valley that day.. it was beautiful and thrilling at the same time.

About Me

I am a teacher of geology at Modesto Junior College and former president of the National Association of Geoscience Teachers, Far Western Section. I have led field trips all over the western United States, and a few excursions overseas, but my homebase is the Sierra Nevada, the Great Valley, and the Coast Ranges of California.